This application claims the benefit of application no. 11-301847, filed in Japan on Oct. 25, 1999, which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates generally to a semiconductor integrated circuit device which contains a plurality of internal circuits driven by separate power supplies, such as multi-function large scaled integrated (LSI) circuit devices, digital and analog hybrid LSI devices, multi-powered digital LSI devices, and more particularly, to a device for protecting the internal circuits from electrostatic discharge which extends over the circuits.
2. Discussion of the Related Art
Semiconductor integrated circuit devices which contain a plurality of internal circuits driven by separate power supplies tend to have an intra-block protection circuit but omit an inter-block protection circuit in order to prevent interference from occurring between the separate power supplies and to prevent noise from propagating from one circuit to another through a power supply system not associated therewith. When the inter-block protection circuit is omitted, this results in complete isolation of the internal circuits as well as complete isolation of power lines connected thereto. Therefore, if surge noise due to electrostatic discharge or the like is introduced on one of the power lines, for example, a power line of a 5-volt system, an undesired potential difference is generated between inter-circuit signal wiring and a power line of the other power supply system, for example, a power line of a 3-volt system, possibly damaging internal elements such as an input element provided in an internal circuit to which the inter-circuit signal wiring is connected.
As countermeasures for preventing the electrostatic breakdown, an inter-block protection circuit has been provided as well between one block comprising an internal circuit and input/output circuits associated therewith, and another block is configured in a similar manner, i.e., between both blocks, when their respective intra-block protection circuits are not sufficient to protect associated internal circuits. Such an inter-block protection circuit includes diodes, transistors and so on, and is connected to both power lines through which different supply voltages are provided (in many cases, a pair or a set of power lines).
As internal elements have become increasingly vulnerable to breakdown as a result of the miniaturization of internal circuits, protection against electrostatic breakdown has been enhanced by increasing the size of intra-block protection circuits, the number of which is smaller than that of internal elements, and increasing the number or size of inter-block protection circuits. However, since the miniaturization and faster operation of internal circuits are still advancing without limits, sufficient protection can no longer be ensured only by repeating the conventional approaches of increasing the protection circuits as described above. Thus, further enhancement in protection of internal circuits from electrostatic breakdown would involve improvements in the characteristics of protection circuits as well as a quantitative improvement of the protection circuits; however, such improvements imply a technical problem as to how an inter-block protection circuit should be configured.
Accordingly, the present invention is directed to a semiconductor integrated circuit device that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
The present invention provides a semiconductor integrated circuit device that is resistant to electrostatic breakdown. The invention also improves the operational characteristics of protection circuits.
Additional features and advantages of the invention will be set forth in the description which follows, and in part, will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the semiconductor integrated circuit device includes a plurality of internal circuits formed in a circuit forming region; a plurality of power lines separately connected to the internal circuits; a signal wire routed between the internal circuits; and a protection circuit connected to the power lines, the protection circuit including a parallel circuit having a first rectifying element formed in a p-type semiconductor region and a second rectifying element formed in an n-type semiconductor region.
In another aspect, the semiconductor integrated circuit device includes a plurality of internal circuits formed in a circuit formation region; a plurality of power lines separately connected to the internal circuits; a signal wire routed between the internal circuits; and a protection circuit connected to the power lines, the protection circuit including rectifying elements formed in portions of a p-type semiconductor region and an n-type semiconductor region, the p-type semiconductor region being adjacent to the n-type semiconductor region.
In a further aspect, the semiconductor integrated circuit device includes a plurality of internal circuits formed in a circuit formation region; a plurality of power lines separately connected to the internal circuits; a signal wire routed between the internal circuits; and a protection circuit connected to the power lines, the protection circuit including a parallel circuit having a first rectifying element formed in a p-type semiconductor region and a second rectifying element formed in a portion of an n-type semiconductor region adjacent to the p-type semiconductor region.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.